[GRASS-dev] Re: 7.x Status Update (Glynn Clements)

[Glynn Clements]

Hamish wrote:

> > > d.what.rast - Replicated with GUI wrapper for r.what
> > > d.what.vect - Replicated with GUI wrapper for v.what
> > > d.where - Built into GUI canvases
> Glynn:
> > I have wondered whether there's any point in
> > cannibalising these as non-interactive programs which accept
> > x/y screen coordinates as arguments.
> 
> r.what already provides a non-interactive d.what.rast, and
> although I am not very familiar with it, v.what exists and
> seems to work. So not much to do here.

Yes, but those modules accept cartographic coordinates, not display
coordinates.

I suppose it's really an issue of whether we need a d.where equivalent
to convert display coordinates into geographic coordinates. If you
have that, d.what.{rast,vect} can be implemented as simple scripts on
top of d.where + {r,v}.what.

The calculation is non-trivial if the region isn't mapped to the full
display (although, currently, there's no way to create sub-frames). 
Also, it may be useful to have a module which uses the same code as
the rest of the display system.

E.g. suppose that you have a web application which generates images
using d.* and uses the image as a server-side image map. The CGI
script will need some way to translate pixel coordinates back to
geographic coordinates.

-- 
Glynn Clements <glynn at gclements.plus.com>